The field of the invention is in electromagnetic wave generating devices and more particularly in the cavity resonator art of laser devices.
Unstable resonators as well as confocal unstable resonators are well known in the laser art. Typical examples of prior art devices are contained in U.S. Pat. Nos. 3,921,096 to patentees Chenausky et al. and 3,969,685 to patentees Chenausky et al.